To solve the problem refusal/incorrect tripping of overcurrent protection caused by power fluctuations of the distribution grid-connected photovoltaic (PV) system, this paper proposes an adaptive strategy based on the LIBSVM for overcurrent protection. The PV system dynamic model which combines with low voltage ride through (LVRT) control strategy is built on the platform of Matlab/Simulink. It also simulates and analyses the characteristics of the short-circuit and the influence on overcurrent protection with the different fault at different locations during the normal operation of PV power output fluctuations. A method is proposed to identify equivalent impedance of the grid-connected PV system during different output based on support vector machines (SVM), a line current adaptive protection criterion is developed, which dynamically adjusts the setting value under the PV system output power and operating modes. The simulation shows that the adaptive strategy can avoid the problem refusal/incorrect tripping of overcurrent protection and improve protection’s performance. This work is supported by National Natural Science Foundation of China (No. 51367017) and International S&T Cooperation Program of China (ISTCP) (No. 2013DFG61520).